1. Field of the Invention
This invention relates to a zoom optical system whose optical axis is bent, and in particular, to a path-bending zoom optical system in which a path-bending prism is placed in order to achieve a slim design with respect to the depth of a digital camera or a personal digital assistant, mounting a zoom optical system.
2. Description of Related Art
In imaging optical systems incorporated in compact cameras, personal digital assistants, and mobile phones which use electronic image sensors such as CCDs, the need for compact design, notably slim design, is emphasized. The optical systems of this type are known by prior art publications described below.
Japanese Patent Kokai No. Hei 10-20191 discloses a zoom optical system constructed with four lens units in which a rectangular prism cemented to a plano-convex lens in the third lens unit is interposed between the third lens unit and the fourth lens unit, and thereby the optical path is bent.
Japanese Patent Kokai No. Hei 9-211287 set forth an optical system in which optical power is imparted to a path-bending prism.